BIOTREATMENT OF SURFACE WATERS TO REMOVE PESTICIDES
Report No FR/K0001

Jun 1992

A. SUMMARY

  1. Members of FWR expressed concern about the contamination of source waters by triazine herbicides and the difficulties of ensuring their removal in water treatment to the levels required by legislation on drinking water quality.

  2. FWR, therefore, commissioned the Biological Laboratory, University of Kent, to investigate the potential for microbiological degradation of the two most common triazine herbicides, atrazine and simazine. The contract, initially for two years from November 1990, has been funded outside the core programme from FWR's investment income.

  3. This interim report gives some background information, summarises the progress to date, and describes the pilot-scale studies planned to start in summer 1992.

  4. Bacteria have been isolated from various sources which can utilise atrazine and/or simazine (at 10mg/l) as a source of carbon and nitrogen. Not all isolates could degrade both herbicides, and some isolates were more effective at 10C than at 30C. The extent and rate of degradation (from an initial concentration of 1g/l), using the most promising isolates , were both inadequate for application to water treatment.

  5. Indications, to date, are that the removal of triazines is much improved in the presence of GAC and appropriate bacterial cultures. The carbon provides a physical support for the bacteria, which then develop an active biofilm that effectively concentrates the herbicides by adsorption and absorption. This provides elevated substrate concentrations for bacterial growth.

  6. Bench-scale experiments are in progress to define the behaviour of the biofilm in GAC packed beds and to measure herbicide degradation at different influent concentrations and retention times.

  7. Results will be used to design a series of pilot-scale experiments, to begin in mid 1992, operating on a 15-minute contact time. The effect of herbicide concentration, background water quality and inoculant establishment will be examined.

    Copies of the Report are available from FWR, price 15.00 less 20% to FWR Members